It is with a heavy heart that we must share the unexpected passing of Reiner Ludwig Stenzel at his home in San Mateo, California, in early December 2023, at the age of 83.
Stenzel was a pioneer in experimental physics, developing several diagnostic techniques as well as conducting seminal research on magnetic field reconnection and antenna/electrode coupling with plasmas. However, his research interests were much wider, as demonstrated by the diverse topics covered by the doctoral theses he supervised: magnetic reconnection, beam/plasma systems, current and heat transport, ion- and beam-plasma turbulence, expanding plasmas, wave excitation, and the transition between magnetized and unmagnetized plasmas.
In addition, Stenzel studied fusor-type discharges and plasma bubbles and fireballs as well as ion sound and lower hybrid and EMHD turbulence. His research has relevance to laboratory and space plasmas, and the latest findings were annually presented at the meetings of the Division of Plasma Physics of the American Physical Society (APS) and the sessions of the Space Physics and Aeronomy division of the American Geophysical Union. The work was also presented regularly at topical conferences as well as at international meetings.
Stenzel was born in Breslau, Germany (now Wrocław, Poland), and received an Abitur from the Gymnasium am Barkhof, Bremen, Germany, in 1959. He was awarded a Studienstiftung des Deutschen Volkes while obtaining his Diplom Ingenieur in 1965 from the then Technische Hochschule Carolo-Wilhelmina in Braunschweig (now Technische Universität Carolo-Wilhelmina zu Braunschweig). He was invited to attend Caltech, where he served as a graduate research assistant and was advised by Roy W. Gould. He was granted an MS in 1966 and a PhD in applied science in 1970.
Shortly after graduating, Stenzel was recruited by A. Y. Wong at UCLA and became an adjunct assistant professor and then assistant research physicist. He simultaneously worked at TRW Inc, where he became a Member of the Staff in 1972. He returned to UCLA full time as an associate professor in 1977 and advanced to professor in 1981, a position he held until retirement in 2012. He was also a visiting scientist at Tokyo University (1980), University of Tromsø (1981), University of Paris-Sud (1995), University of Innsbruck (2007, 2009, and 2012), and the Max Planck Institute for Plasma Physics (2015).
Stenzel was elected an APS Fellow in 1993 for his pioneering work. Even though he and his wife had moved to the Bay Area to be close to his children and grandchildren, he continued experimental work as a research professor until the pandemic made periodic visits to UCLA impractical. Stenzel was one of the best experimentalists of his time, with 226 publications and countless conference presentations.
Norbert Wild, Stenzel’s first PhD student, recalls that “working in the plasma physics lab under his guidance would be the foundation of my eventual career as an experimentalist in industry. Reiner’s brilliance and artistry in designing, building, calibrating, and fielding plasma diagnostic probes was inspirational. In my work, I still refer to Reiner’s class notes on plasma turbulence from a research tutorial he gave in 1979, where he would show us how to read and interpret recently published results on various types of plasma instabilities. His standard of excellence was uncompromising, and I have used his paradigm of ‘work on it until it works right’ in many different aspects of my life.”
As a second-year PhD student, David Whelan almost transferred to Caltech to work with Roy Gould but was informed by his adviser that a new and excellent UCLA faculty member had studied under Gould. After meeting with Stenzel, Whelan was impressed by the quality of his research and joined his group. Whelan recalls that “under Herr Professor Doktor Stenzel’s tutelage I developed the experimental skills and theoretical understanding required to be a modern experimental physicist and an innovation leader. Reiner’s demand for perfection in everything he studied and required in each of his students has enabled my ability to create new technologies and systems that serve our national defense and, for me, the confidence to take on leadership roles in the Boeing Company and the DoD’s DARPA.”
Garnick Hairapetian recalls that “Reiner’s love of plasma physics, work ethic, and ability to design and build intricate and elegant plasma diagnostic tools were always awe-inspiring for me. Reiner was always generous with his time and always available to his students, whom he always treated as his colleagues. Our daily lunch meetings with Reiner on the west lawn of the Powell Library were always illuminating, intellectually challenging, and a welcome break from the graduate school daily grind.”
Stenzel loved nature, a passion he shared with the members of his local Boy Scout Troop, eventually becoming its Scout Master, a position he held until 1991. He also was a leading member of the Ski Mountaineers Section of the Los Angeles Chapter of the Sierra Club, serving as Outings Chair, Vice Chair, and Chair. He received the group’s Outings Service Award in 2000. His leadership is evident in the stories shared in his numerous trip reports, preserved in various web pages, from the early 1990s onward.
His love of the outdoors was inherited by his children, who joined him in many hikes over the last 20 years. He also shared it with his students. Hairapetian recalls that “Reiner was an accomplished Telemark skier. One of my fondest memories of Reiner was when he suggested we visit the Loveland Ski Area while attending a space plasma conference in Denver, Colorado. However, we had to be back on the same day for important presentations in the afternoon session. So we woke up at the crack of dawn, drove to Loveland, started skiing when the lifts opened, and then drove back to Denver before the presentations started.” At the age of 73, Stenzel hiked the entirety of the Pacific Crest Trail over two seasons, a feat his daughter described as “his dream escapade … one more item checked off of his bucket list.”
In lieu of gifts or flowers, the family would like to further the study of physics with donations to the following organizations: Studienstiftung.de, UCLA and Caltech Physics graduate programs, Sierra Mountaineering programs related. Please send all correspondence to [email protected].
Yung Chan, Chris Tousculp, Garnick Hairapetian, David Whelan, and Norb Wild also contributed to this obituary.
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